This invention relates to pneumatic actuator systems of the type utilizing rotary, pneumatic vane motors.
Certain instances of use of actuator systems such as in aircraft environments place a premium upon the weight, reliability, and compactness of unit design. For these reasons, therefore, it has been found in many instances that pneumatic actuator systems have distinct advantages over other types of power systems such as electrical or hydraulic systems. Exemplary of hydraulic actuator system and/or elements thereof to which the above described problems apply may be found in the following U.S Pat. Nos. 2,056,909; 2,345,920; 2,393,223; 2,653,551; 2,711,698; 2,777,396; and 3,260,210.
Utilization of a pneumatic actuator system provides the advantage of lower weight and more economical construction. One distinct advantage of a pneumatic system is that it may utilize a source of bottled gas or the like as a potential energy power source. Rotary, pneumatic vane motors are utilized to transform the potential energy of the stored, pressurized gas into rotational kinetic energy. Previous vane motors of the type referred to characteristically are expansion type motors wherein power is derived both from the presence of the pressure differential across the vane as well as expansion of the pressurized gas. While such expansion type vane motors extract a maximum amount of power from the pressurized gas, certain resulting limitations are necessarily incoporated within the vane motor itself. More particularly, such vane motors, by virtue of expansion of the incoming pressurized gas, must necessarily permit radial movement of the vanes of the motor while the vanes are subject to a pressure differential. The resulting frictional forces and side loads placed upon the vanes severely restricts the life and reliability of the motor. Furthermore, such known pneumatic actuator systems are the "open center" type which introduce an unnecessary loss of pressurized gas.
An exemplary application of such a pneumatic actuator system is in driving the flight control devices on an aircraft. Elements such as the flight stabilizing fins on a missle must be precisely controlled for efficient flight performance. Accordingly, the actuator system must necessarily provide the capability of extremely precise positioning of the power output actuator member.